This work was carried out in collaboration with the Cushman laboratory (Diabetes Branch, NIDDK) and Dr. Arthur Sherman (LBM, NIDDK). Obesity is often, but not always associated with insulin resistance. Insulin resistance is a fundamental characteristic of type II diabetes mellitus, even before the appearance of hyperglycemia, independent of the presence of obesity. An abnormality in adipose cell turnover has been postulated to play the unifying role in these metabolic relationships. To investigate the dynamics of adipose tissue, J. Mackellar in the Cushman laboratory developed a micro-biopsy protocol to sample adipose tissue from a rat at intervals of several days. Data was obtained under two conditions: normal and treated with thiazoledinediones. [unreadable] [unreadable] The normal animals showed adipose tissue dynamics on their own so our first goal was to mathematically characterize this development. Towards this end, we considered a variety of modeling approaches, and finally settled on computing the power spectrum of the cell size data. With some statistical analysis, we have found that there is a statistically significant periodicity in adipose tissue dynamics of about 40 days in normal untreated animals. This work is being prepared for publication.[unreadable] [unreadable] Our next goal is to use the same type of technique to characterize the changes in adipose tissue dynamics due to TZD treatment, relative to control.